use cond-> to conditionally add keys to a map

cond->.clj

;; Use cond-> to conditionally add keys to a map
;; http://grimoire.arrdem.com/1.6.0/clojure.core/cond-%3E/

(let [a 3
      b nil
      c false
      d "word"]

  (cond->
   {}
   a
   (assoc :a a)

   b
   (assoc :b b)

   c
   (assoc :c c)

   d
   (assoc :d d)))

;; => {:d "word", :a 3}